We don't belong here.

[Angrboda]

You've concluded that a thing being unnatural is bad, and therefore that our existing on earth is bad because it's unnatural. The flaw is in your initial assumption that if a thing is unnatural it is necessarily bad. There are many unnatural things that are actually good (let me count the ways). So the problem with your argument has nothing to do with whether our survival on earth is natural or not, but rather your assumption that if it is not natural it is bad. Once you remove the flawed assumption, your argument collapses.